1. Technical Field
The present invention relates to an illuminating device and a liquid crystal display apparatus having the illuminating device.
2. Related Art
Generally, in liquid crystal display apparatuses, a technique (it is also referred to as “local dimming”) of adjusting luminance of a backlight, which is an illuminating device, has been used as a technique for improving contrast of a display image.
For example, Japanese Unexamined Patent Application Publication No. 2007-293339 discloses a technique that adjusts luminance of each light guide plate block in a way that an illumination region of the backlight is divided into a plurality of light guide plate blocks and luminance of LED (light emitting diode) disposed on each light guide plate block is adjusted.
However, in the technique disclosed in Japanese Unexamined Patent Application Publication No. 2007-293339, light emitted from the LED is light of point-light source. In this point of view, in order to turn light emitted from the LED into uniform illuminating light through the light guide plate, it is necessary to increase diffusion of light by elongating an optical path of the light guide plate. Because of this, an area of the light guide plate can not be decreased, and a size of each light guide block is restricted. Accordingly, a range of the display image capable of adjusting luminance of the backlight can not be decreased. As a result, luminance of the display region can not be minutely adjusted.